Pattern formation aspects of electrically charged tri-stable media with implications to bulk heterojunction in organic photovoltaics

¹ Department of Solar Energy and Environmental Physics, Swiss Institute for Dryland Environmental and Energy Research, Blaustein Institutes for Desert Research, Ben- Gurion University of the Negev, Sede Boqer Campus Midreshet Ben-Gurion 8499000, Israel
² Department of Mathematics, Technion - Israel Institute of Technology - Haifa, 3200003, Israel
³ Department of Physics, Ben- Gurion University of the Negev - Be'er Sheva 8410501, Israel

Received: 25 October 2018
Accepted: 17 January 2019

Abstract

A common thread in designing electrochemically based renewable energy devices comprises materials that exploit nano-scale morphologies, e.g., supercapacitors, batteries, fuel cells, and bulk heterojunction organic photovoltaics. In these devices, however, Coulomb forces often influence the fine nano-details of the morphological structure of active layers leading to a notorious decrease in performance. By focusing on bulk heterojunction organic photovoltaics as a case model, a self-consistent mean-field framework that combines binary (bi-stable) and ternary (tri-stable) morphologies with electrokinetics is presented and analyzed, i.e., undertaking the coupling between the spatiotemporal evolution of the material and charge dynamics along with charge transfer at the device electrodes. Particularly, it is shown that tri-stable composition may stabilize stripe morphology that is ideal bulk heterojuction. Moreover, since the results rely on generic principles they are expected to be applicable to a broad range of electrically charged amphiphilic-type mixtures, such as emulsions, polyelectrolytes, and ionic liquids.